1. Field of the Invention
This invention relates to a mobile cleaning device. More particularly, this invention relates to a remote controlled chopping machine for cutting and chopping solids buildup on the interior floor of hydrocarbon storage tanks of the type used in petroleum refineries and chemical plants.
2. Brief Description of the Related Art
Petroleum refineries, chemical plants, petroleum and chemical stock farms, and similar plants, are normally provided with large cylindrical storage tanks having diameters of from about 20 to about 300 feet and heights of from about 50 to about 100 feet and closed to the atmosphere by floating or fixed roofs. With the passage of time, and particularly when the tanks are used to store crude oil, sedimentation and fouling of the tank surfaces will occur.
Conventionally, a gang of workmen enter the tank through an entryway adjacent the bottom of the tank and manually operate high pressure hoses, similar to the hoses used in fighting fires, in order to wash down the inside of the tank. Suction lines disposed on the bottom of the tank are used to remove the wash water and sediments collected by the water. It is generally necessary for the workmen to use respirators and wear protective garments. As a consequence, a workman can work inside the tank for only a very limited time because of the debilitating working conditions, and must then leave the tank to rest.
U.S. Pat. No. 4,817,653, issued Apr. 4, 1989 to Richard W. Krajicek et al, and assigned to the assignee of the present invention, is directed to solving the problems associated with washing down the inside of the above described tanks. The '653 patent describes an essentially self-contained mobile water washing robot which is remotely operable, thereby negating the need for operating personnel to be in close proximity of the cleaning nozzles and other high pressure lines during water wash cleaning operations. U.S. Pat. No. 4,817,653 is incorporated herein by reference for all respects and purposes.
However, even with the improvements in tank cleaning disclosed in the '653 patent, the problem of solids buildup on the floor of the storage tank still exists. This is a particular problem when solids such as coke, sludge, or granite accumulate and harden over a period of time. In general, these sludge-like materials form mounds or large cakes on the bottom surface of the tank, especially in areas where there is little or no turbulence, and must be broken into smaller pieces for disposal. Heretofore, these materials were cut by laborers into fragments by repeated strokes with a pickax, and then shoveled or otherwise "mucked out". Thus, while the disclosure of '653 patent eliminated much of the dangerous, undesirable in-tank labor, improvements still need to be made. It is an object of the present invention to provide a hydraulically powered, remotely controlled, movable chopping device for breaking up the high-solids material deposits on the bottom of the above described types of hydrocarbon storage tanks.
Accordingly, the present invention is directed to an apparatus for chopping waste, such as sludge formed on the bottom of the interior of oil storage tanks, and comprises modular components that can be separately moved inside a storage tank and then conveniently assembled inside the tank to form a workable apparatus.